The overall objectives of this project are to examine the effects of normal human plasma lipoproteins on a variety of lymphocyte functions and responses and to explore the mechanisms responsible for the observed effects. The first goal evaluates the effects of all classes of normal lipoproteins (VLDL, IDL, LDL, and HDL) on immune functions; including T and B cell rosette formation, the production of leucocyte migration inhibitory factor, antibody formation to T dependent and T independent antigens; the graft versus host reaction and the homograft reaction. This proposal will also examine the effect of these same lipoprotein classes on the functions of different immunocompetent cells, as well as the effects of lipoproteins from patients with abnormalities of lipoprotein metabolism, including Type III hyperlipoproteinemia, familial combined hyperlipidemia, and biliary cirrhosis on similar immune functions. The possibility that a single subclass of lipoproteins is responsible for immunoregulation will be explored. The effects of the lipid and apoprotein components of the plasma lipoproteins will be studied to provide insights into the biochemical mechanisms involved in lipoprotein regulation of the immune response.